Textures and colors not imported from OBJ file when using Cycles render
As far as I know, cycles does not yet support importing materials due to the great difference in the way materials are designed in cycles.

There are some plugins such as blender material to cycles node converter

http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Material/Blender_Cycles_Materials_Converter

I would recommend importing while under blender internal renderer, than either hand creating the cycles nodes, or using this plugin to generate them.